Potential ambient ozone impact on ecosystems in the Czech Republic as indicated by exposure index AOT40

The AOT40 exposure index developed within the context of the UN-ECE as a critical level is a tool commonly used in Europe to assess the geographical areas with vegetation potentially at risk due to elevated ambient ozone concentrations. Using the ambient ozone data recorded within a regular monitoring network in the Czech Republic, the AOT40 values both for forests and crops/semi-natural vegetation for vegetation periods of 1994–2001 were calculated. The critical level exceedance fields for threshold values set as 10ppmh for forests and 3ppmh for crops and semi-natural vegetation have been derived using the ARC/INFO system and its module GRID. The IDW method is used for interpolation. Effect of altitude change on ozone concentration has been taken into account. Maps for two extreme years 1994 and 1997 (both as to meteorology and ozone concentrations measured) are presented in this paper. The results indicate that the above threshold values are generally exceeded over nearly the entire territory of the country throughout the period under review, even in years with meteorological conditions unfavourable for ambient ozone formation. The years differ, however, in the value of threshold level exceedance: in years with lower ozone concentrations (e.g. 1997), the threshold value for forests (10ppmh) is exceeded almost two times at the maximum while in years with plentiful ozone (e.g. 1994 and 1995), the threshold level over the most of the territory is exceeded 2–3.5 times. The threshold value for crops/semi-natural vegetation (3ppmh) in years with lower ozone concentrations is exceeded five times at the most while in years with plentiful ozone it might be exceeded as much as eight times. The quantification of actual extent of ozone impact is an extremely complicated issue and the role of all different factors (both genetic and environmental) contributing to plant response on ozone should be recognised.